FM Transmitter Circuit using Transistors

FM transmitters are one one of the basic RF circuit you could easily build at home and of course you can even play with these kinda circuits. The above circuit is one of the simplest and most basic FM transmitter you could build. Even though this FM transmitter circuit supplied with only 5V it is capable of covering the range of around 300 meters.

WORKING OF FM TRANSMITTER CIRCUIT DIAGRAM:

The above circuit consists of two stages where one stage formed by the first transistor Q1 is meant to amplify the audio signal picked by means of a simple microphone. Thus Q1 amplifies the signal obtained and feed it to the second stage that is a oscillator built around Transistor Q2.

Output from Q1 is fed to the base of the Q1 where the oscillator built operates around 100MHz. The audio signal from the first stage modulates the resonant frequency of the oscillator circuit. The modulated wave is then fed into the antenna. The frequency of the above circuit can be adjusted by varying the capacitance value in the VC1. You can also alter the components based on your operating frequency range.

NOTE:

Place the transmitter about 10 feet away from the FM radio. to avoid the effect of harmonics.

You can also increase the range of the transmitter by increasing the supply voltage fed to it.